Reversible programmer for electric circuits

ABSTRACT

A device for providing repetitive pulses having adjustable width and spacing including a drive motor, a cam pin rotatable with the output shaft of the drive motor and a second cam pin carried with the first pin but angularly manually adjustable relative thereto. A switch mounted adjacent the paths of travel of the pins causes the motor to periodically reverse as the pins sequentially operate the switch back and forth. One or more other switches are operated by one or both of the cam pins to control external load means. The angular relationship of the pins is adjustable by moving one pin, through a friction clutch, relative to the other. Increasing the angle between pins increases the pulse spacing, and adjustment of an output switch position alters the pulse duration.

United States Patent 1 Gruenwald 1 June 12, 1973 REVERSIBLE PROGRAMMER FOR ELECTRIC CIRCUITS [75] Inventor: Bjorn J. Gruenwald, Easton, Pa.

[73] Assignee: Alpha Press Electronics, Inc., Alpha,

[22] Filed: June 22, 1971 [21] Appl. No.: 155,581

Primary ExaminerJ. R. Scott Attorney-Roy1ance, Abrams, Berdo & Kaul [57] ABSTRACT A device for providing repetitive pulses having adjustable width and spacing including a drive motor, a cam pin rotatable with the output shaft of the drive motor and a second cam pin carried with the first pin but angularly manually adjustable relative thereto. A switch mounted adjacent the paths of travel of the pins causes the motor to periodically reverse as the pins sequentially operate the switch back and forth. One or more other switches are operated by one or both of the cam pins to control external load means. The angular relationship of the pins is adjustable by moving one pin, through a friction clutch, relative to the other. Increasing the angle between pins increases the pulse spacing, and adjustment of an output switch position alters the pulse duration.

2 Claims, 23 Drawing Figures PATENIEU 3.739.113

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REVERSIBLE PROGRAMMER FOR ELECTRIC CIRCUITS This invention relates to timing apparatus, and, more specifically, to an electromechanical apparatus for providing a repetitive cyclic output having adjustable predetermined characteristics.

The prior art includes many examples of efforts to construct timing devices of an electromechanical type which are capable of producing cyclic outputs having predetermined patterns. Most of these involve motors, cams and switches, the cams being designed to actuate these switches in accordance with some prearranged program.

However, it has been generally necessary to construct each timer in accordance with the desired program, the timers so constructed being somewhat special purpose devices and incapable of significant adjustment. Although most such timers have the capacity for replaceable cams and the like there does not appear to be any simple device in the prior art for producing a cyclic output having adjustable on and off times so that the timer can function as a general purpose device.

Accordingly, it is an object of the present invention to provide an electromechanical timer having means for producing a repetitive cyclic output in which the ratio of on time to off time is adjustable and in which the absolute value of off time is similarly adjustable.

A further object is to produce a timing device in which repetitive output pulses are produced, the spacing between the pulses being adjustable and the duration of the pulses being constant throughout the range of pulse spacing adjustment.

Briefly described, the apparatus of the invention includes a rotary drive means, a structure capable of rotary or arcuate motion between preselected angularly spaced limits, the structure being driven by the drive means. The drive means is reversible and cam means carried by the structure and rotatable therewith activates the reversing means and also provides a cyclic output. The means carried by the structure constitutes two cam devices which are angularly spaced from each other, the angular spacing being adjustable to alter the spacing between output pulses.

In order that the manner in which the foregoing and other objects are attained in accordance with the invention can be understood in detail, particularly advantageous embodiments thereof will be described with reference to the accompanying drawings, which form a part of this specification, and wherein:

FIG. 1 is a plan view, in partial section, of an apparatus in accordance with the invention;

FIG. 2 is a section along lines 2-2 of FIG. 1;

FIG. 3 is a front elevation of a portion of the apparatus of FIG. 1;

FIG. 4 is a schematic diagram of a typical switch usable in the apparatus of FIG. 1;

FIGS. 5 and 6 are schematic diagrams of alternative arrangements for the electrical connection of the drive means;

FIGS. 7A-F and 8A-D are timing diagrams illustrating the modes of operation of the apparatus of FIGS. 1-6;

FIG. 9 is an elevation, in section, of a further embodiment of an apparatus in accordance with the invention;

FIGS. l0A-C are timing diagrams illustrating the operation of the apparatus of FIG. 9; and

FIG. 11 is a diagram showing the angular relationship in the apparatus of FIGS. 1-6 and 9.

As shown in FIG. 1, a preferred embodiment of the apparatus includes a housing 10 which contains a drive device such as a conventional reversible electrical motor, operable in either direction. The motor 10 has an output shaft 11 which is rotatable with the motor in either direction. For convenience, the motor is shown mounted to a panel or mounting bracket 12, the bracket having an opening 13 through which shaft 11 protrudes.

A cylindrical body 14 is coaxially mounted on shaft 11 and is firmly attached thereto by a pin or set screw 15 so that the body rotates with shaft 11. A pin 16 protrudes radially outwardly from body 14, pin 16 being attached to the body by a threaded connection or, for example, by an adhesive.

The distal end of body 14 is provided with an internally threaded axially inwardly extending hole 17 which is threaded and dimensioned to receive a machine screw 18, screw 18 having a large head. A disc 19 is provided with a central opening through which the shaft of bolt 18 extends, the disc being held thereby against the flat end of body 14. A pin 20 can be driven through the disc and the end of body 14 to prevent rotation of the disc relative to the body.

It will be recognized that the structure thus far described, including the motor, shaft 11, pin 16, body 14, disc 19 and bolt 18 all rotate together in either direction in accordance with the manner of energization of motor 10.

An additional structure is carried by body 14 and disc 19 and includes an annular ring 21. Ring 21 is generally rectangular in cross section but has an inwardly extending annular recess 22 forming a shoulder which bears against the peripheral margin of the outer surface of disc 19. A second disc 23, which is of larger diameter than disc 19,has a central opening 24 which loosely surrounds body 14. Disc 23 is held against the back surface of annular ring 21 between the ring and bracket 12 by. any suitable fastening means such as a standard machine screw 25. An axial pin extends axially from the back face of ring 21 toward bracket 12, passing through disc 23. Pin 26 has an externally threaded end 27 which threadedly engages an axially inwardly extending hole 28 through the back surface of ring 21. An annular shoulder 29 is provided on pin 26 at a suitable position to assist in retaining ring 23 firmly engaged with the back surface of ring 21. A pointer 30 is formed on, or attached to, the inner cylindrical surface of ring 21.

A mounting bracket 35 is attached to bracket 12 and supports a sensitive switch 36. Switch 36 can be any conventional switch of the type generally referred to as micro" action switches or sensitive switches which require relatively little force for actuation. Switch 36 is provided with an actuating arm 37, depression of which operates a button 38 which extends through the housing of the switch and mechanically moves the operating switch mechanisms therein. The contents of the switch are, in general terms, well known and will not be described in mechanical detail. However, it should be noted that the switch can be a single-pole, single-throw, normally open or normally closed, or a single-pole, double-throw usable in either mode.

An additional bracket 40 is mounted on bracket 12 and supports a sensitive switch 41 which is also a switch requiring little force for its actuation, but is of a different variety in that it should include at least one singlepole, double-throw contact set. Switch 41 is provided with an actuating arm 42 which, when moved, operates a toggle 43 to operate the switch mechanism within the switching housing.

As will be recognized from the above description, the apparatus includes a drive means for rotating an assembly wherein the assembly constitutes two parts which normally move together but which can be adjusted relative to each other. Further, the assembly includes two cam members or pins, one on each of the two subportions of the assembly so that the pins can be adjusted relative to each other. In particular, body 14, bolt 18 and disc 19 are fixed to and always move with shaft 11 and the motor. However, the subassembly including ring 21, disc 23 and pin 26 can be slipped relative to disc 19, adjusting the position of pin 26 relative to pin 16. It will be observed that a friction washer 32 is provided between discs 19 and 23 to normally maintain these two in fixed relationship. However, by simply grasping ring 21 and rotating it, an adjustment can be accomplished.

As shown in FIG. 3, the nature of the adjustment can be observed by observing the relative positions of pointer 30, which is mounted on and moves with ring 21, and an arrow 31 which is provided on the outer face of disc 19. Arrow 31 is always aligned with pin 16 whereas pointer is always aligned with pin 26.

It will also be observed from FIG. 1 that actuating arm 37 is axially spaced from pin 16 and never comes in contact with that pin. However, pin 26 is capable of moving arm 37 and operating switch 36.

Conversely, switch 41 can be operated by either pin. Pin 16 is axially spaced from bracket 12 the same distance as actuating arm 42 of switch 41 so that pin 16 engages the arm and moves it whenever it is rotated to the appropriate angular position. Furthermore, pin 26 axially extends sufficiently close to plate 12 to permit the switch to be operated as that pin approaches the angular position of the operating arm, again operating the switch.

The manner of operation can be best seen by referring to FIG. 2. In this figure switch 41 should be regarded as the reversing switch, the function of that switch being to reverse the direction of the drive means whenever it is moved from one position to the other. Also, since switch 41 is a bistable, or toggle switch, it remains in whichever position it is moved to by whichever pin causes its movement.

To discuss the operation of the apparatus consider energization of the drive means in a counterclockwise direction as viewed in FIG. 2. Pins 26 and 16 will then be driven in the counterclockwise direction, the path of pin 26 being approximately defined by the circular outline of motor housing 10. As pin 26 rotates approximately 95 from the position it occupies in FIG. 2, arm 42 of switch 41 will be moved from the position shown to its alternative stable position, shown in dotted lines in FIG. 2. At that point, the motor will be reversed and pins 26 and 16 are driven in the clockwise direction until pin 16 engages arm 42 at which time switch 41 is moved to its other stable state, causing the drive means to be reversed to its originally assumed direction of motion. This institutes a new cycle of operation, which cycle continues as long as the motor is energized.

Now consider the operation of switch 36. Each time switch 26 approaches the reversing location, arm 36 of switch 36 is moved, causing the switch, which is monostable in nature, to be either opened or closed. Switch 36, being the output switch, then produces a pulse the duration of which is determined by the time required for pin 26 to move through the angle defined by the first actuation of switch 36 and the actuation of switch 41 and then back again until switch 36 is returned to its original state.

A typical switch usable as switch 36 is shown in FIG. 4, wherein the actuating button 38 is schematically shown mechanically coupled to the movable contact of a single-pole, double-throw switch. Clearly, connections can be made to the center terminal and either or both of the terminals connected to the fixed contact so that single-pole, double-throw or single-pole, singlethrow with either normally open or normally closed operation can be accomplished. Thus, the output constitutes several possible combinations.

However, it will be assumedin discussions hereafter that the switch is connected so that terminals 37 and 46 are connected to a load device and a source of voltage. The switch is then operated as a normally open, singlepole, single-throw switch and will provide outputs as shown in the subsequent figures.

FIGS. 5 and 6 are simple schematic diagrams showing possible connections of the drive means. In FIG. 5, the reversing switch indicated generally at 41 is connected to either of two windings of the motor 10, the motor being reversible depending upon which winding is energized.

In FIG. 6, a two-motor approach is used, one motor being connected to drive the output shaft 11 in one direction and the other motor being connected to drive the shaft in the opposite direction. It will also be recognized that motors designed for use with either alternat ing or direct current sources can be employed.

The operation of the apparatus can be further understood by observing the wave form and timing diagrams in FIG. 7 A-D. FIG. 7A constitutes a timing diagram with equal time intervals being displayed by the graduations along the abscissa. When the wave form is in its lowest position the time interval of clockwise motion is indicated, while counterclockwise motion is indicated when the wave form is in its upper position.

Along with FIG. 7A, consider the output diagram illustrated in FIG. 7B which shows the positions of switch 36 as detected at terminals 45 and 46, FIG. 4. When the diagram is in the upper position the switch is closed (i.e., conductive) between those two terminals, the lower position being the off or open position.

It will be observed that actuation of the output switch occurs when pin 26 approaches the end of one interval of counterclockwise movement such as interval 50, initiating the beginning of an output pulse 51. Then, after the motor has reversed and commenced moving in the clockwise direction, switch 36 is released, terminating pulse 51. The motor and apparatus carried thereby then moves in the clockwise direction for interval 52 until pin 16 causes reversal again, initiating interval 53, near the end of which an output pulse 54 is produced. The cycle is then repeated for intervals 55 and 56 and pulse 57, and so forth for so long as the apparatus is energized.

Now, assume that ring 21 is rotated relative to disc 30 and 31 and pins 26 and 16. This location is illustrated in FIG. 2 by the dotted line 58, indicating the new position of pin 26. The operation of the apparatus with this adjusted position is shown in FIGS. 7C and 7D, FIG. 7C being a timing diagram similar to FIG. 7A and FIG. 7D showing the output produced between terminals 45 and 46 as in FIG. 78. It will be observed that each output pulse is of the same duration as pulses 51, 54 and 57, the duration of each such pulse being determined solely by the relative positions of switches 36 and 41 and their actuating arms. However, the intervals 59, 60 and 61 are shorter than the off intervals between pulses in FIG. 78 because the total cycle time has been reduced as seen in FIG. 7C.

Adjustment of ring 21 in the opposite direction to move pin 26 to a position represented approximately by the dotted line 62 in FIG. 2 results in diagrams such as those shown in FIGS. 75 and 7F. It will be seen in FIG. 7E that the absolute time intervals of clockwise and counterclockwise motion are greatly increased, thus increasing the off time between output pulses. However, the duration of the output pulses remains the same for the reasons discussed above.

FIGS. 8A-E illustrate alternative modes of operation of the apparatus. FIG. 8A is a diagram showing the cycle time of counterclockwise and clockwise movement of the drive means and the apparatus carried thereby. FIG. 8B is a diagram similar to FIGS. 7B and 7D, showing the output produced by switch 36.

FIG. 8C illustrates a further feature of adjustability which can be incorporated in the apparatus whereby the duration of the on pulse or output pulse can be adjusted. This adjustability can be incorporated simply by arranging for adjustment of the relationship of actuating arms 37 and 42. One manner is which this can be accomplished is by providing an arcuate slot 33 for one of the fastening devices associated with bracket 35. By loosening a nut 34 (FIG. 1) bracket 35 can be loosened enough to rotate the bracket about the fixed fastener, permitting the arm 37 to be moved relative to arm 42, thereby causing switch 36 to be closed earlier and opened later than in FIG. 8D. It will be observed, however, that so long as switch 36 is closed during the reversal time the output pulse will necessarily straddle the reversal as shown in all of FIGS. 7 and 8.

FIG. 8D illustrates the phase inversion which can be accomplished simply by using the normally closed contacts of the output switch shown in FIG. 4.

Still other arrangements of the apparatus can be provided simply by altering the mounting arrangement of the switches. For example, as shown in FIG. 9, switch 36 can be mounted farther away from switch 41 so that the actuating arm of switch 36 is operated to turn the switch on and off again before the cam which operates that switch contacts the reversing arm of switch 41. Then, on its return trip, switch 36 is again operated. This is illustrated in FIGS. A and 108 wherein FIG. 10A again shows the reversing cycle of the drive means and FIG. 10B illustrates the output of switch 36 when connected to terminals 45 and 46 as previously discussed.

Still further, additional switches such as switch 65 can be positioned in other locations in the path of travel of either pin 16 or pin 26 to be actuated as the pin passes the actuator thereof. The result of such an addition is the production of output pulses at other 10- cations with respect to the rotation wave form of FIG.

10A, the pulses such as might be produced by switch 65 being shown in FIG. 10C.

In FIGS. 10B and 10C it will be recognized that the time spacing for the pulses is a function of the angular relationship between the two pins and the angular relationship between the adjustable limits of motion of the pins and the switch actuators. As shown in the angle diagram of FIG. 11, if the total angle between pins is the angle then the total cycle time is equal to that angle divided by the angular rate of travel of each pin r. This time t, is shown in FIG. 10A. The interval between the beginning of such a cycle and the output pulse produced by switch 65 would then be equal to the angle a divided by r, illustrated in FIG. 10C as the interval t,. In similar fashion, the interval to production of an output pulse by switch 36 is the angle B divided by r, or interval t as shown in FIG. 10B. Likewise, interval t to the reversal point is equal to the angle 7 divided by r. The time relationships of the other output pulses can be similarly calculated.

Although the motor circuits shown in FIGS. 5 and 6 are suitable for continuous operation, it is possible to operate the apparatus in single cycles or half cycles with appropriate switching circuits, and it can be convenient to do so. The foregoing apparatus can be combined with manually or externally operable switch or pulsing means and stop switches which will cause the motor to terminate its rotation at the end of each cycle, or half cycle, and await a signal from the external source. Circuits for accomplishing this will now be described with reference to FIGS. 12 and 13.

In FIG. 12 a circuit is shown for operating the apparatus in the half cycle mode wherein the motor, when energized, rotates in one direction until it reaches the limit of motion in that direction as determined by the switch actuator at which time it stops and awaits an external signal. In the circuit of FIG. 12 a motor is provided with windings 76 and 77, each of the windings being designed to drive the motor in one direction. A capacitor 78 is provided to supply the necessary phase shift in a well known manner. A series-parallel circuit is connected in parallel circuit relationship with winding 77, this circuit including a conventional semiconductor diode 79 in series with the parallel circuit including a conventional diode 80 and the winding of an electromagnetic relay 81. Winding 81 controls a singlepole, double-throw contact set indicated generally at 82, this contact set having a movable contact which is movable between fixed contacts identified as a and b. The movable contact is in the b position, as shown, when winding 81 is de-energized.

Diode 80 is included to absorb the de-energization current when winding 81 is de-energized.

A similar circuit is in parallel with winding 76 of motor 75, this circuit including a conventional semiconductor diode 83 in series circuit relationship with a parallel circuit including a diode 84 and a relay winding 85 which controls the operation of a single-pole, double-throw contact set indicated generally at 86. The movable contact of contact set 86 is also movable between fixed contacts identified as a and b, b again being the de-energized position.

The shaft of motor 75 is connected to mechanical means 87 for actuating a single-pole, double-throw bistable switch indicated generally at 88. Switch 88 has a movable contact which is movable between fixed contacts c and d, depending upon the operation of the motor shaft and actuating means 87. It will be recognized that the actuating means can be the combination of pins and levers shown, for example, in FIG. 2, switch 88 then being analogous to bistable switch 41.

The movable contact of switch 88 is connected at terminal 89 to a source of AC line voltage such as 115 volts AC. Terminal 89 is also connected to a starting circuit which includes a momentary contact reset switch indicated generally at 90. Terminal 89 is connected to the normally open fixed contact of that switch set, the other fixed contact being connected to one terminal of a fixed resistor 91. The movable contact of switch 90 is connected to one terminal of a capacitor 92, the other terminal of which is connected to the other terminal of resistor 91 and to the anode electrodes of two conventional semiconductor diodes 93 and 94. The cathode of diode 93 is connected to winding 81 and the cathode of diode 94 is connected to winding 85.

Fixed contacts b of switches 82 and 86 are connected through a diode 95 to a relay circuit 96 which is operated by the timing circuit and controls a load device. The relay circuit shown is, of course, merely an example. The other side of relay circuit 96 is connected to the other AC line terminal 97 as are the other terminals of the relay windings and motor windings discussed heretofore.

The operation of the circuit of FIG. 12 can be described by commencing with the switches in the positions shown. As such, the relays and motor are deenergized and the motor is in one extreme position of its rotary movement, that position at which switch 88 was moved to its position. To commence operation, switch 90 is momentarily closed, permitting capacitor 92 to be charged through two parallel circuits including diodes 93 and 94 and relay windings 81 and 85. Because of the relatively large current which flows at the initial stages of charging a capacitor, and with suitable circuit values chosen, the relays are both energized, causing contact sets 82 and 86 to switch to their a positions. It will be seen that energization of the relays immediately establishes a circuit for one of motor windings 76 and 77, depending upon the position of switch 88. As shown, the circuit is completed from terminal 89 through switch 88 to the c contact, through switch 86 and its a contact and through motor winding 76. The motor is accordingly caused to rotate in the direction which, at its limit, will cause switch 88 to move to its d position. However, before that position is reached, it will be seen that capacitor 92 will shortly become charge, or else switch 90 is released or both. Release of switch 90 causes capacitor 92 to discharge again through resistor 91, but regardless of which event occurs first, the means for initially energizing relays 81 and 85 is removed. At that time a circuit has already been established through switches 88 and 86 to winding 76, and a holding circuit is thus provided through diode 83 and winding 85, maintaining that relay energized. Insufficient voltage appears on the side of the circuit including diode 79 and winding 81 to maintain that set in its energized condition and contact set 82 returns to its d position. The circuit remains with the motor running and relay winding 85 energized until the motor reaches its limit of motion at which switch 88 is moved to its d position. This breaks the circuit through switch 86 to windings 76 and 85, thereby stopping the motor and de-energizing winding 85. Contact set 86 returns to its d position and the circuit is again dormant until an external signal, in the form of the momentary closing of switch 90, again initiates the operation of the circuit which is essentially the same as described above except that winding 77 and relay winding 81 are energized, causing the motor to rotate in the opposite direction.

The circuit of FIG. 13 is somewhat similar in principle but involves a slightly different sequence of operation. In FIG. 13 a motor is provided with windings 101 and 102 and a capacitor 103, the windings being energizible individually to drive the motor in opposite directions. Winding 102 is connected to the d fixed contact of a single-pole, double-throw contact set indicated generally at 104, the movable contact of which is operated by the motor shaft at the limits of its motion. It will be observed that a movable contact is in connection with fixed contact 0 when the apparatus is in its dormant or rest condition. The movable contact of contact set 104 is connected to one terminal 105 of an AC source and also to one fixed contact of a momentary contact push button switch 107 which is analogous to push button switch 90. A capacitor 108 is connected in series circuit relationship with switch 107, the switch and capacitor being paralleled by a discharge resistor 109. A conventional semiconductor diode is connected in series circuit relationship with the switch and capacitor and with the energizing winding 112 of an electromagnetic relay. Energizing winding 112 actuates a single-pole, double-throw contact set indicated generally at 113, the movable contact of the set being movable between fixed contacts a and b, contact b representing the de-energized condition. A diode 114 is connected in parallel relationship with winding 112, and a diode 115 is connected in series with the winding. It will be noted that diode 115 completes a circuit be tween contact a of contact set 113 and winding 112 so that a latching circuit can be completed. The movable contact of contact set 1 13 is connected to fixed contact 0 of contact set 104.

Contact b of the contact set 1 13 is connected through a diode 116 to a load relay 117 or other suitable utilization device. It will be noted that winding 101 of the motor is also connected to contact a of set 113 and is therefore energized simultaneously with relay winding 112.

In operation, push button 107 is operated to complete a circuit between 105, through the push button and capacitor 108 and diode to winding 112, the charging current of the capacitor causing energization of winding 112 and actuation of contact set 113. As soon as the relay has been actuated a circuit is available from terminal 105 through contact set 104 in the position shown in FIG. 13, through contact set 1 13 in its energized position to contact a so that the relay is maintained in its energized condition after the push button is released or the capacitor has charged, and winding 101 of the motor is also energized. Thus, the motor runs until it causes operation of contact set 104 to the position in which the movable contact is against contact d. At that point the relay holding circuit is lost and the relay returns to its de-energized position. Winding 102 is then energized through the circuit from terminal 105, switch 104, winding 102 to terminal 106, causing the motor to run in the opposite direction. The motor runs until it reaches its limit of motion at which time contact set 104 is returned to its 0 contact and the system again becomes dormant, awaiting a new initiation by closing contact set 107.

It will be seen that in the operation of the circuits of FIGS. 12 and 13 a precisely timed interval is initiated by operation of a push button switch, the interval in the circuit of FIG. 12 constituting rotation of the motor in one direction from one of its limits to the other, and the interval in FIG. 13 being defined by the movement of the motor from one limit to the other and back again. Thus, the FIG. 12 circuit can be referred to as a half cycle circuit while FIG. 13 constitutes a full cycle circuit.

While certain advantageous embodiments have been chosen to illustrate the invention it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.

What is claimed is: 1. A timer comprising first means mounted for reciprocating arcuate motion between preselected angularly spaced limits;

means for repetitively driving said first means alternately in both directions between said limits;

means for reversing the direction of said means for driving upon arrival of said first means at each of said limits; and means carried by said first means for actuating said means for reversing and for providing a cyclic output, 1 1

wherein said means carried by said first means includes a first cam mounted in fixed relationship to said first means; and

a second cam mounted for movement with respect to said fist cam, said second cam being angularly adjustable with respect to said first cam to adjust the angular spacing between said angularly spaced limits;

and wherein said second cam comprises a disc fixedly attached to said output shaft;

an adjustable disc frictionally engaging said fixed disc; and

a cam surface carried by said adjustable disc.

2. A timer comprising first means mounted for reciprocating arcuate motion between preselected angularly spaced limits,

means having an output shaft for repetitively driving said first means alternately in both directions between said limits;

said first means including a disc attached to said output shaft for movement therewith; and

a second disc carried by said output shaft, said second disc being angularly adjustable relative to said first disc;

means for reversing the direction of said means for driving upon arrival of said first means at each of said limits; and means carried by said first means for actuating said means for reversing and for providing a cyclic output, said means carried by said first means including a first actuating pin attached to said output shaft; a second actuating pin carried by said second disc;

and means for adjusting the angular spacing between said preselected angularly spaced limits. 

1. A timer comprising first means mounted for reciprocating arcuate motion between preselected angularly spaced limits; means for repetitively driving said first means alternately in both directions between said limits; means for reversing the direction of said means for driving upon arrival of said first means at each of said limits; and means carried by said first means for actuating said means for reversing and for providing a cyclic output, wherein said means carried by said first means includes a first cam mounted in fixed relationship to said first means; and a second cam mounted for movement with respect to said fist cam, said second cam being angularly adjustable with respect to said first cam to adjust the angular spacing between said angularly spaced limits; and wherein said second cam comprises a disc fixedly attached to said output shaft; an adjustable disc frictionally engaging said fixed disc; and a cam surface carried by said adjustable disc.
 2. A timer comprising first means mounted for reciprocating arcuate motion between preselected angularly spaced limits, means having an output shaft for repetitively driving said first means alternately in both directions between said limits; said first means including a disc attached to said output shaft for movement therewith; and a second disc carried by said output shaft, said second disc being angularly adjustable relative to said first disc; means for reversing the direction of said means for driving upon arrival of said first means at each of said limits; and means carried by said first means for actuating said means for reversing and for providing a cyclic output, said means carried by said first means including a first actuating pin attached to said output shaft; a second actuating pin carried by said second disc; and means for adjusting the angular spacing between said preselected angularly spaced limits. 